For digital printing, the printing press has at least one inkjet print head or several inkjet print heads, with, for example, different printing inks such as Cyan (C), Magenta (M), Yellow (Y), and/or Black (K), and a rotary table for receiving the three-dimensional object, wherein the rotary table is configured for placing the object in front of the inkjet print head or several inkjet print heads, and for rotating it about the axis thereof, in order that the surface to be printed of the three-dimensional object is guided past the inkjet print head or the inkjet print heads for digital printing, in which the ink drops are sprayed onto the surface when required (drop-on-demand process).
Three-dimensional objects such as bottles or cans made, for example, of glass, plastic, and/or metal, have until now been labeled or printed using screen printing. For this, a direct digital decoration of the surfaces of the three-dimensional objects using inkjet print heads, which work on the drop-on-demand principle, has been possible for some time now.
The digital printing presses used for this are known in several embodiments. For one, there are the single printing presses (for quantitatively smaller output requirements), in which one object each is fixed and digitally printed. Further, there are the synchronized presses, in which a plurality of single printing presses are placed side by side, and several objects standing on one station each are printed simultaneously. In such synchronized presses, the output of the whole machine corresponds to the multiple of the individual output of a single station, each of which, in particular, can be equipped with single printing presses. A characteristic feature of the synchronized presses is the simultaneous change to several three-dimensional objects to be printed in the individual stations. Also, cyclically operating machines are usually designed such that the individual inks or colors to be printed are printed one after the other in successive stations. As a rule, the output of such a synchronized press is limited by the speed of a print head, which specifies the time for the printing on a three-dimensional object. This time determines the cycle time significantly.
Besides these, there are also solutions which enable significantly higher outputs (in terms of quantity) than synchronized presses. There are two embodiments known for this. One groups together complete single printing presses, in which the entire printing is done on one station, side by side, on a carousel. The other reproduces the output of one or more colors through a plurality of single printing stations for each color on a separate carousel each. Such types of machines are described as carousel machines, in which the (cycled printing in itself) is done in single printing presses of a rotating carousel. This enables continuous handling of the three-dimensional objects to be printed.
One thing common to all the solutions is that the printing of a logo or a security feature using special inks is not possible, or is possible only to a limited extent, because these special inks are mostly not suitable for printing using inkjet print heads.
Often, such an overprint on such decorations is, however, necessary, which has to be done using special inks, such as for example, the application of a deposit logo in the case of non-returnable containers for beverages in Germany. As a rule, such inks are security inks, which guarantee protection against counterfeiting, and are not suitable for processing in inkjet print heads due to their structure. Such prints are, as a rule, made on the girth circumference of a three-dimensional object, such as a non-recyclable bottle or can, since they must be non-detachable. As a rule, such logos or special prints are standardized and are not subject to any frequent changes in the print design, unlike digital printing, which is designed for variable data and decorations.
The question of a solution for three-dimensional objects, which are digitally decorated, did not arise, due to the usage, until now, of labels or sleeves, which are produced in offset printing, gravure printing or flexographic printing. Nevertheless, it may be required to provide basically digitally decorated or printed three-dimensional objects additionally with an overprint, which requires the application of non-inkjet printing capable printing inks.
The DE 10 2007 020 635 A1 describes the use of security ink in an identification system for an object.
The DE 29 38 026 A1 discloses a pad device with a matrix printer as a fixed pad element.
WO 03/106177 A2 discloses a device for machining the surface of parts with a plurality of different machining stations, at which different machining processes are carried out. The machining processes comprise a printing of the parts using inkjet print heads, as well as using screen printing, offset printing, flexographic printing, or gravure printing processes. Besides this, the device has a rotary transfer machine configured as a conveying unit, which conveys the parts to the predefined desired positions at the stationary machining stations. After conveying, the rotary transfer machine is at a standstill for the duration of machining on the parts. After the machining, i.e., in cycles, the rotary transfer machine is then rotated further, to handle the next part in the respective machining station.
From WO 2009/018892 A1, different devices for printing of containers are known. One device describes a direct printing of the container with inkjet print heads, which can be connected or disconnected for the partial printing, wherein an inkjet print head can be moved out of the printing position and another print head can be moved into the printing position. WO 2009/018892 A1 also discloses a device different from this for printing containers using a transfer printing, in which the printing is done using inkjet print heads on transfer pads (and not directly on the container), which transfers the image by rolling off on the respective container. In the process, the transfer pads and the containers are moved at different speeds, which roll off the transfer pads onto the surface of the containers.
In US 2009/0205516, a process is disclosed for the direct printing of bottles using inkjet printing, wherein variations in the bottle dimensions due to manufacturing tolerances are reconciled by determining the dimensions of the bottles and calculating the correction values for the control.
In DE 10 2013 208 061 A1, a device of the generic kind for printing containers is described.